Mechanism for adjusting the inclination of backrests in chairs and arm-chairs, particularly in office chairs

ABSTRACT

The invention relates to a mechanism for an office chair or arm-chair, in which control means for the backrest inclination and spring means for biasing the backrest to the position of minimum inclination are provided, in which at least one stepped stop block can be moved in a controlled manner, a step of said block being suitable to interfere with a member connected to the backrest when the same is being inclined, in order to limit the stroke of said member between the position of minimum inclination of the backrest and a position of interference of the member connected to the backrest with a selected one of the block steps. The invention also relates to a method for transforming a locking mechanism to an end-of-stroke mechanism.

The present invention relates to a mechanism for controlling the movement of a chair/arm-chair backrest, particularly in office chairs, in which means are provided for controlling the backrest inclination, as well as spring means biasing the backrest to the position of minimum inclination.

Mechanisms of the above-mentioned type are known in which the backrest is inclined by the user and then locked in the selected position by acting on a knob, acting through releasable mechanical connections to generate a locking interference with a structural member that is connected with the backrest, in both directions and in any of a plurality of positions.

The object of the present invention is now to provide a mechanism to be applied to chairs and arm-chairs, particularly office chairs of the above-mentioned type, in which the inclination movement of the backrest, which is always controlled by the user pushing on the latter, is limited as desired, so that more positions of maximum inclination can be defined, the backrest automatically returning to the position of minimum inclination when the user's weight is no longer rested thereon. In other words, the mechanism according to the invention allows the user to define in advance two or more points of maximum inclination for the backrest, thereafter the backrest can be inclined only to the maximum angle such as determined by the user's action.

A further object of the invention is a method for transforming a know type of locking mechanism such as discussed above in a mechanism for limiting the backrest inclination. The mechanism and the method of the invention further achieve the above-mentioned objects in a particularly easy and cost-effective manner.

The above-mentioned objects are achieved by means of a type of mechanism and method having the functionalities as described above, which are characterized according to the annexed claims.

FIGS. 1 to 3 of the drawings are perspective views of three exemplary mechanisms for office chairs and the like, which have been modified for obtaining said end-of-stroke to the backrest.

More specifically, referring first to FIG. 1, a usual mechanism 10 for an office chair or arm-chair or the like is illustrated, which has been changed only in those parts intended for locking the inclination of the backrest such that an end-of-stroke is fitted for the backrest instead of this locking, such as discussed above.

To this purpose, the lever 11, which is placed within the mechanism and connected to the seat such as to axially move when the backrest is inclined, is no longer locked in each position being reached, for example by means of a stop member that can be fitted between two adjacent teeth of a plurality of teeth carried by the lever, by the user acting on a knob 12 and a control rod 13.

To transform the locking device in an end-of-stroke device, it is sufficient that a rod 13 having a polygonal section, such as in 14, is provided and a block 15 is mounted thereon having a set of steps 16 facing the free end of the rod 11 such as to interfere with the movement of the free end thereof, the stroke of the rod being thus limited according to the step facing the same, which is selected by the user acting on the knob 12.

In the mechanism 17 of FIG. 2, a lever 18 (in dotted lines) is connected to the support 19 of the backrest and moves longitudinally according to the inclination of the latter. In the case of a locking mechanism, the lever is provided with a plurality of teeth, a stop device actuated by the user interfering therewith. On the other hand, in the case illustrated, the lever 18 is swingably pivoted in 20 and is controlled to raise from a cam 21 that can be actuated by a user by means of a knob 22 and a rod with a polygonal section 23. Then, the lever 18 has a pivot 24, which according to the inclination of the lever 18, is suitable to interfere with one of the steps of a fixedly mounted stepped block 27, in order to limit the stroke of the lever 18, and accordingly the inclination angle of the backrest in a consequent manner.

In FIG. 3 there is illustrated a further embodiment 28 in which two stepped blocks 29 are provided each acting in a parallel manner with one of their steps, directly on the support 30 of the backrest. Also in this case, the two blocks 29 are controlled by a rod having a polygonal section 31 that can be actuated by the user through a knob (not illustrated).

The rod 31 carries a pair of toothed pinions 32 which act on racks 33 integral with the blocks 29 to move the latter in the longitudinal direction and consequently have a desired one of the steps 34 at the free end of the support 30 in order to consequently limit the stroke of the latter and the seat. 

1. A mechanism for a chair or arm-chair, particularly of the office type, in which control means for the backrest inclination and spring means for biasing the backrest to the position of minimum inclination are provided, characterized in that the control means for the backrest inclination comprise at least one stepped stop block, each step thereof being suitable to interfere with a member connected to the backrest when the same is being inclined, means being provided for moving the stop block or the member connected to the backrest into several discrete positions, in order to limit the stroke of said member between the position of minimum inclination of the backrest and a position of interference of said member connected to the backrest with a selected one of the block steps.
 2. A mechanism according to claim 1, characterized in that said member connected to the backrest is a support of the backrest.
 3. A mechanism according to claim 1, characterized in that said member connected to the backrest is a lever connected to the support of the backrest.
 4. A mechanism according to claim 1, characterized in that said means for moving the stop block consist of control means for the block longitudinal movements.
 5. A mechanism according to claim 4, characterized in that the block longitudinal movements are controlled in a direction perpendicular to the step interference surfaces, by means of a knob acting on a rack and pinion mechanism.
 6. A mechanism according to claim 1, characterized in that said means for moving the stop block consist of control means for the block rotations.
 7. A mechanism according to claim 6, characterized in that the rotation control means consist of a knob suitable to rotate a rod carrying the block.
 8. A mechanism according to claim 1, characterized in that said means for moving the member connected to the backrest are means for moving a lever connected to the backrest and interfering with one of the steps of a fixed block, by means of a pivot or projection.
 9. A mechanism according to claim 8, characterized in that said lever moving means consist of a cam that is moved by the rotations of a drive knob and suitable to raise the lever in a direction substantially parallel to the step interference surfaces.
 10. A mechanism according to claim 9, characterized in that it comprises elastic means for returning the lever to the position of minimum inclination.
 11. A mechanism according to claim 1, characterized in that a pair of stop blocks acting in a parallel manner are foreseen.
 12. A method for transforming a mechanism for an office chair or arm-chair, comprising means for locking the inclination of the backrest in a plurality of positions, as well as spring means for biasing the backrest to the position of minimum inclination, in a mechanism in which the backrest inclination stroke is limited to several preset values, characterized in that the backrest locking means are replaced with one or more stepped blocks according to claim
 1. 13. A method according to claim 12, characterized in that each stepped block is suitable to interfere with a lever corresponding to the locking lever in the non-transformed mechanism. 